usr: libc: Add math.h + musl math impl portexpt

Signed-off-by: Ian Moffett <ian@osmora.org>

1 files changed, 24 insertions, 0 deletions

diff --git a/lib/libc/src/musl-math/exp10f.c b/lib/libc/src/musl-math/exp10f.c
new file mode 100644
index 0000000..74f8909
--- /dev/null
+++ b/lib/libc/src/musl-math/exp10f.c
@@ -0,0 +1,24 @@
+#define _GNU_SOURCE
+#include <math.h>
+#include <stdint.h>
+#include "weak_alias.h"
+//#include "libc.h"
+
+float exp10f(float x)
+{
+	static const float p10[] = {
+		1e-7f, 1e-6f, 1e-5f, 1e-4f, 1e-3f, 1e-2f, 1e-1f,
+		1, 1e1, 1e2, 1e3, 1e4, 1e5, 1e6, 1e7
+	};
+	float n, y = modff(x, &n);
+	union {float f; uint32_t i;} u = {n};
+	/* fabsf(n) < 8 without raising invalid on nan */
+	if ((u.i>>23 & 0xff) < 0x7f+3) {
+		if (!y) return p10[(int)n+7];
+		y = exp2f(3.32192809488736234787031942948939f * y);
+		return y * p10[(int)n+7];
+	}
+	return exp2(3.32192809488736234787031942948939 * x);
+}
+
+weak_alias(exp10f, pow10f);